Coil configuration for an electromagnetic warhead influence firing system

ABSTRACT

A coil configuration for a torpedo warhead exploder influence firing system for use against surface and submarine targets consists of an orthogonal coil configuration where the transmit coils are surface mounted on the warhead section of the torpedo, and two receiver coils are mounted perpendicular to each other, one vertical and the other horizontal to the torpedo axis. The transmit coils generate an electromagnetic field around the region of the torpedo which induces eddy currents in a nearby hull. The eddy currents in the hull then induce a voltage in the receiver coils, indicating the presence of a ship.

United States Patent Cioccio et al.

45] Oct. 24, 1972 [54] COIL CONFIGURATION FOR AN ELECTROMAGNETIC WARHEAD INFLUENCE FIRING SYSTEM [72] Inventors: Armand Cioccio; Gee-in Goo, both of Silver Springs, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: April 27, 1971 [21] Appl. No.: 137,907

[52] US. Cl. ..102/l8, 102/19.2, 102/702 [51] Int. Cl. ..F42b 23/26, F42b 21/38 [58] Field of Search ..102/18, 19.2, 70.2 P; 324/40 [56] References Cited UNITED STATES PATENTS 2,981,184 4/1961 Kennel etal ..102/l8 3,450,986 6/ 1969 Chapman et a1 ..324/40 Chubbet et al. ..102/18 Hafner 102/702 P X Primary Examiner-Benjamin A. Borchelt Assistant ExaminerJames M. Hanley Attorney-R. S. Sciascia, J. A. Cooke and R. J. Erickson ABSTRACT A coil configuration for a torpedo warhead exploder influence firing system for use against surface and submarine targets consists of an orthogonal coil configuration where the transmit coils are surface mounted on the warhead section of the torpedo, and two receiver coils are mounted perpendicular to each other, one vertical and the other horizontal to the torpedo axis. The transmit coils generate an electromagnetic field around the region of the torpedo which induces eddy currents in a nearby hull. The eddy currents in the hull then induce a voltage in the receiver coils, indicating the presence of a ship.

12 Claims, 9 Drawing Figures PATENTEDum 24 I972 SHEET 1 0F 3 IN VENTORS Armand Cz'occz'o Gee -Jn G00 BY 577p ATTORNEY PATENTED um 24 I972 SHEET 2 OF 3 INVENTOR Armand Ci occio Gee In 600 PATENTED E 24 I973 3. 699,889

sum 3 or 3 INVENTORS Armand Gz'occz'o Gee 1n G00 COIL CONFIGURATION FOR AN ELECTROMAGNETIC WARI-IEAD INFLUENCE FIRING SYSTEM BACKGROUND OF THE INVENTION This invention relates generally to electromagnetic warhead influence systems, and more particularly to the coil configuration for a torpedo warhead exploder influence firing system for use against surface and submerged targets.

There are two types of electromagnetic warhead influence systems, the passive and active systems. The passive system merely seeks electromagnetic signals, while the active system generates its own electromagnetic field and seeks a signal return from the target. Since the active system generates its own field, it seeks a return signal of the same frequency as the transmitted field. With the aid of electronic signal processing, the active system can therefore be made highly resistance to countermeasures relative to the passive system. Active systems employ transmitting coils to radiate the electromagnetic field into the surrounding water medium, and receiving coils to receive the eddy current induced return signals from the target. The active type coil configuration can be separated into two categories, the RXE and the RXEO systems. The RXE coil configuration consists of an orthogonal coil configuration where the transmitting coil is coaxial to the torpedo axis while the receiving coil is mounted vertically to the torpedo axis at a short distance from the transmitting coil. By maintaining the receiving coils aligned perpendicular to the transmitting coils, ideally there is no directly induced voltages in the receiving coils from the transmitting coils. However, from a practical standpoint, it is impossible to completely eliminate all directly induced voltages. Therefore, nulling is achieved in the RXE coil system by adjusting the receiving coil position and manually adjusting an inphase" and quadrature-phase control. Obviously, each such coil system has to be hand tailored for the particular torpedo. In addition, the RXE system suffers from a highly directional directivity pattern, resulting in an intolerable variation in range and course trajectory.

The RXEO coil system design is subdivided into two classes: the REXO vertical look" and the RXEO 360look systems. The RXEO vertical look system is similar to the RXE system. It too consists of orthogonal transmit and receive coils, except that the transmit coil is surface mounted in the afterbody of the torpedo, while the receiving coil is mounted in a plastic torpedo nose. The longer base line (separation between transmitting and receiving coils) enables this system to minimize the directly induced receiver voltages while the plastic shell allows the receiving coil to have a wider angle of detection. Although the directly induced receiver voltage is reduced, the long baseline creates an alignment problem which, in turn creates nulling problems. The RXEO 360 look coil configuration consists of a coaxial, surface mounted transmitter coil located in the afterbody of the torpedo, and a coaxial receiver coil mounted in the nose section of the torpedo. Since the transmit and receiver coils are coaxial, a large voltage is directly induced in the receiver coil by the transmitted signal. This large directly induced voltage is nulled by placing a small coil near the receiver coil which generates an opposite-polarity field. In addition, metal plates are used to provide quadraturephase components. Although this coil configuration is highly desirable for use against both surface and submarine targets because of its 360 directivity pattern, there is an unresolved problem of eddy current in sea water which makes its use unfeasible.

To increase the operational sensitivity of the prior art systems, the torpedo section containing the receiver coils has to be made of material that does not greatly attenuate the returning of the magnetic signal. ln addition the shell material has to be made of material capable of withstanding the pressures at great depths. Consequently, titanium is generally used for this purpose, but its great expense adds considerably to the cost of the torpedo. Since the RXEO 360 look system has the transmitter coils and receiver coils located in separate sections of the torpedo, replacement of either section cannot be made without completely realigning the coils so as to produce the appropriate geometric configuration and transmit and receive patterns with the desired nulls.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a new and improved coil system for a warhead influence firing system. Another object of the present invention is to provide a coil system for a torpedo warhead influence firing system that can be used against surface and submerged targets.

Still another object of the present invention is the provision of a coil system for a torpedo warhead influence firing system that can be uniquely packaged into a single section of the torpedo.

Still another object of the present invention is to provide a coil system for a torpedo warhead influence firing system that can be packaged in an inexpensive shell.

A further object of the present invention is to provide a coil system for a torpedo warhead influence firing system that is insensitive to eddy currents in sea water.

A still further object of the present invention is to provide a coil system for a torpedo warhead influence firing system that can be easily interchanged without affecting performance of the warhead system.

Briefly, these and other objects of the present invention are attained by providing several alternative embodiments of coil configurations, for use in a torpedo warhead influence firing system, each of which achieves all of these objects. In all of the embodiments, the transmitter coils and receiver coils are located in the same section of the torpedo, and each embodiment provides a 360 directivity pattern. In a first group of embodiments, four transmitter coils are bar coils and are embedded in pockets at intervals on the surface of the torpedo section, and the receiver coils are axially displaced from the transmitter coils. In a second group of embodiments, the transmitter coils are square coils mounted within the torpedo section and there is no axial displacement between the receiver coils and transmitter coils.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the invention and many of the attendant advantages thereof will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connected with the accompanying drawings wherein:

FIG. 1 is a pictorial view of a coil configuration having transmitter coils located at 90 intervals in pockets on the surface of a torpedo section and two crossed bar type receiver coils located internally within the torpedo section;

FIG. 2 is a pictorial view of a coil configuration having four transmitter coils located at 90 intervals in pockets on the surface of a torpedo section and a pair of vase-shaped receiver coils located internally within the torpedo section;

FIG. 3 is pictorial view of a coil configuration having four transmitter coils at 90 intervals located in pockets on the surface of a torpedo section and having four bar type receiver coils forming a square pattern located internally within the torpedo section;

FIG. 4 is a pictorial view of a coil configuration according to the present invention having four transmitter coils spaced at 90 intervals in pockets on the surface of a torpedo section, and four bar type receiver coils spaced at 90 intervals in pockets on the surface of the torpedo section;

FIG. 5 is a pictorial view of a coil configuration in accordance with the present invention wherein four transmitter coils are spaced at a 90 intervals in pockets along the surface of a torpedo section, and four flat spiral receiver coils are spaced at 90 intervals along the surface of the torpedo;

FIG. 6 is a pictorial view of a coil configuration in accordance with the present invention wherein the transmitter coils are formed of square coils located internally within a torpedo section and the receiver coil is a square coil positioned inside of the transmitter coil configuration;

FIG. 7 is a pictorial view of a square coil that is used in the embodiment of FIG. 6;

FIG. 8 is a pictorial view of a coil configuration in accordance with the present invention, wherein the transmitter coils are square coils located internally within a torpedo section, and the receiver coil is wound on the surface of the torpedo section;

FIG. 9 is pictorial view of a coil configuration according to the present invention having a square coil transmitter coil configuration located internally within a torpedo section, and having a single bar coil receiver coil located inside of the transmitter coil configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like reference characters designate corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, a coil configuration for a warhead influence firing system is shown as consisting of a torpedo section 10, such as a warhead section, four transmitter coils 12 surface-mounted on torpedo section in shallow pockets 1 1 and two receiver coils 14 longitudinally spaced from transmitter coils 12 by a distance L and mounted internally within torpedo section 10. As disclosed in US. Pat. Application Ser. No. 154,241, filed June 14, 1971 by Eugene H. Beach et al on an invention entitled Warhead Influence Firing System, a sur' face ship or submarine may be detected by transmitting electromagnetic radiation of fixed frequency, which incluces eddy currents in the hull of a target ship or submarine, receiving the return electromagnetic radiation generated by these eddy currents, and processing the signal to verify that a target vessel has been detected. The coil configuration of FIG. 1 is adaptable for use with this system, or any other active warhead influence firing system but the electronic circuitry for generating and processing such signals does not form a part of this invention and therefore need not be specifically disclosed herein. Transmitter coils 12 are mounted so that two of the coils lie along a vertical axis 13 of the torpedo section, and the other two coils lie along horizontal axis 15 of the torpedo section. Receiver coils 14 are mounted so that one coil is aligned along vertical axis 13 of the torpedo section, and the other coil is aligned along horizontal axis 15 of the torpedo section. All four transmitter coils are driven in parallel with an audio frequency sinousodal signal, as described in the aforementioned U.S. Pat. Application Ser. No. 154,241, and all of the transmitter coils are otherwise identical, so that a symmetrical transmit pattern is generated about torpedo longitudinal axis 17. As a result of the symmetrical transmit pattern and the coil geometry, a voltage null is produced in receiver coils 14 from the direct electromagnetic radiation of transmitter coils 12. It should be understood that a minimum of four transmitter coils are required to produce a symmetrical transmit pattern about the torpedo axis. However, both the vertical pair of transmitter coils and the horizontal pair of transmitter coils independently produce nulls in receiver coils 41. Transmitter coils 12 are wound on ferromagnetic cores 16, and, similarly, receiver coils 14 are wound on ferromagnetic cores 18.

The separation distance L between transmitter coils l2 and receiver coils 14 affects the shape of the signature received from the target and also effects the sensitivity of the system. As L is decreased, the sensitivity is lowered, and, at L==0, the signature will have a zero crossing when the coils are directly under the center of the target. The maximum sensitivity is obtained when L is equal to 3/4 of the desired standoff distance from the target to the torpedo. Since the transmitter coils and receiver coils are rigidly mounted in the same section of the torpedo, there is essentially no relative movement between them during the course of the torpedo run, and, consequently, minimal noise is produced. This factor coupled with a large number of turns on receiver coils 14 produces very high sensitivity. Returning electromagnetic radiation from the target strikes the shell of torpedo section 10 which induces eddy currents therein. These currents generate a field in opposition to the incoming field from the target, which effectively attenuates the incoming field. Since the sensivitity of the system according to the present invention is very high, attenuation in the shell of torpedo section 10 may be tolerated, without adversely affecting system performance. As a result, materials that attenuate electromagnetic radiation may be used for the shell, such as forged aluminum. These materials have the advantage of greatly reduced expense over materials that only minimumly attenuate electromagnetic radiation, such as titanium.

FIG. 2 provides an alternative coil configuration, wherein receiver coils 14 are wound on vase-shaped cores 20 having large end pieces 22. This configuration provides more core material for receiver coils 14, thereby enabling more magnetic flux to be gathered, which, in turn, increases the sensitivity of the coil configuration. The geometry of transmitter coils 16 and receiver coils 14 is the same in this embodiment as in the embodiment of FIG. 1. In both FIG. 1 and FIG. 2, the orthogonal crossed-coil configuration of the receiver coils produces a 360 directivity pattern about the longitudinal axis of the torpedo. The receiver coils of FIGS. 1 and 2 are connected in quadrature.

FIG. 3 illustrate another alternative embodiment of the coil configuration of this invention. Transmitter coils 12 are arranged on torpedo section in the same manner as in the previous embodiments. The receiver coils consist of four bar coils 24, 26, 28, and 30 arranged in a square pattern that is completely contained within the shell of torpedo section 10 and is symmetrical about longitudinal axis 17. Coils 24, and 28 are parallel to horizontal axis 15 and coils 26 and are parallel vertical axis 13. Coils 24 and 28 are connected series opposing while coils 26 and 30 are also connected series opposing, and one pair is connected in quadrature with the other pair. Using this arrangement for the receiver coils there is less noise than in the other embodiments, since noises in one direction are cancelled in either pair of coils by the series aiding connectors. It would be noted that since the receiver coils in this embodiment are symmetrical about the longitudinal axis of the torpedo, the receiver coil configuration has a 360 directivity pattern.

FIG. 4 illustrates another embodiment of this invention for an influence warhead firing system coil configuration. In this embodiment, transmitter coils 21 are positioned in the same manner as in the previous embodiments. Four receiver coils 32, 34, 36 and 38 are spaced at 90 intervals about longitudinal axis 17 and are placed in shallow pockets on the surface of torpedo section 10. Coils 32 and 36 are parallel to torpedo vertical axis 13, and coils 34 and 38 are parallel to torpedo horizontal axis 15. Each receiver coil is a bar coil whose longitudinal axis is perpendicular to the longitudinal axis of the transmitter bar coils. In addition, the receiver coils are separated from transmitter coils 12 by a distance L, as described hereinbefore. Receiver coils 32 and 36 are connected series opposing, and receiver coils 34 and 38 are also connected series opposing, and one pair is connected in quadrature to the other pair. Thus, the receiver coil connections are the same as the receiver coil connections in the embodiment of FIG. 3. By having the receiver coils surface mounted on the shell of torpedo section 10, however, a stronger signal is received than in the embodiments of FIGS. 1-3 since it is not attenuated by the forged aluminum shell of torpedo section 10.

FIG. 5 illustrates another embodiment, of the present invention, wherein transmitter coils 12 are mounted in the same manner as in the previous embodiments, but, again the receiver coils have been modified. Four flat spiral wound receiver coils 42, 44, 46, and 48, are

mounted on the surface of torpedo section 10. The four receiver coils are spaced at 90 intervals about longitudinal axis 17 of the torpedo, with coils 42 and 46 located along torpedo vertical axis 13, and coils 44 and 48 located along torpedo horizontal axis 15. The receiver coils have no cores, but are flat wound in a spiral on top of a permaloy backing, and then laminated with an adhesive to maintain physical rigidity of the coil. The receiver coils are then either secured to the surface of torpedo section 10, or place in very shallow pockets on the surface of torpedo section 10. As in the previous embodiments, the receiver coils are separated from transmitter coils 12 by a distance L, which may vary anywhere from the maximum length of torpedo section 10 to zero, depending upon the sensitivity described and the type of signature desired. Receiver coils 42 and 46 are connected series opposing, and receiver coils 44 and 48 are connected series opposing. One pair of receiver coils is then connected in quadrature with the other pair as in FIGS. 3 and 4. Since the receiver coils are positioned symmetrically about torpedo longitudinal axis 17, the receiver directivity pattern is also symmetrical about torpedo longitudinal axis 17. This configuration provides greater sensitivity per coil turn, since all of the receiver coil windings are on the surface of torpedo section 10.

In FIGS. 1-5, two of the transmitter coils are positioned along torpedo vertical axis 13, and two of the transmitter coils are positioned along torpedo horizontal axis 15. It should be understood, however, that transmitter coils 12 may be positioned symmetrically at other locations on torpedo section 10. If it is undesirable to have surface mounted coils along vertical axis 13 or horizontal axis 15 because of possible damage by the torpedo launch tube mechanism, each of transmitter coils 12 could be located, for example, at 45 angles to axes l3 and 15. By moving each of transmitter coils 12 45, the only operational difference will be that all four transmitters coils are necessary to produce a voltage null in the receiver, whereas when the transmitter coils 12 are aligned along axes l3 and 15, each pair of transmitter coils will produce a separate voltage null. This difference, however, will not adversely affect system operation.

FIG. 6 illustrates an alternative coil configuration for a warhead influence firing system, which is substantially different from the previous embodiments. In this embodiment, four square coil transmitter coils 50, 52, 54, and 56 are internally positioned within the shell of torpedo section 10. As illustrated in FIG. 7, each square coil" consists of a ferromagnetic core 58, having four legs 60, 62, 64, and 66 which define a hollow square. Coil windings 68 are wound about the external, peripheral surfaces of core 58. Referring again to FIG. 6, transmitter coils 50 and 54 are positioned in planes parallel to torpedo horizontal axis 15, while transmitter coils 52 and 56 are positioned in planes parallel to torpedo vertical axis 13. The edges of the transmitter cores are touching, so that the resulting geommetrical configuration is a cube. A square coil" receiver coil 70 is positioned internally within the transmitter coil cube configuration and is centrally located therein and is positioned orthogonally to all four transmitter coils and lies in plane perpendicular to torpedo longitudinal axis 17. The transmit and receive patterns of this configuration are orthogonal to the transmit and receive patterns of FIGS. 1-5, but, a 360 look capability is still obtained. Since the transmitter coils are located within torpedo section 10, more attenuation of the radiated signal occurs than in the transmit coil configuration of FIGS. 1-5. Consequently, this coil configuration requires a torpedo shell which does not attenuate the signal. Additionally, since there is no longitudinal separation between the transmitter coils and receiver coil 70, the target signature will have a zero crossing, as explained hereinbefore. Transmitter coils 50 and 54 are connected in parallel, and transmitter coils 52 and 56 are connected in parallel. One pair is driven 90 out of phase relative to the other pair. In this manner, a field vector is obtained that rotates at the driving frequency of the transmitted signal, and it is this rotation that produces the 360 directivity pattern.

FIG. 8 illustrates another embodiment of the invention that is similar to the embodiment of FIG. 6. Here, the transmitter coil configuration is identical to the transmitter coil configuration of FIG. 6, but the receiver coil configuration differs. A receiver coil 72 consists of a ring core fitted externally around torpedo section 10, and wound circumferentially. Alternatively, the receiver coil winding can be wound directly on the shell of torpedo section 10. Since receiver coil 72 is externally mounted and there is no attenuation of the signal reaching it, a stronger return signal is received. As a result, this configuration is more sensitive than the configuration of FIG. 6.

Referring now to FIG. 9, another embodiment of the present invention is illustrated. Here, the transmitter coil configuration is identical to that of FIGS. 6 and 8, but, again, the receiver coil configuration differs. A bar type receiver coil 74 is positioned internally within the transmitter coil cube configuration, wherein the bar core is aligned along torpedo longitudinal axis 17. This configuration requires a non-attenuating shell, such as fiberglass, or titanium since both receiver coil 74 and the transmitter coils are located internally within torpedo section 10. This configuration offers the advantage, however, of having a more nearly uniform 360 directivity pattern than the other embodiments since the radiation lobes of the transmit pattern are complimented by the radiation lobes of the receive pattern.

Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings. For example, a vertical look directivity pattern could be obtained by eliminating the vertically aligned receiver coils in FIGS. 3-5. Similarly, a vertical look directivity pattern could be obtained by eliminating the horizontally aligned transmitter coils in FIG. 1-5. Numerous other directivity patterns can be obtained by either adding or subtracting transmitter coils and receiver coils. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A coil system for a torpedo electromagnetic influence firing system comprising:

a plurality of transmitting coils mounted on a section of the torpedo for transmitting electromagnetic radiation; and

a plurality of receiving coils mounted on said torpedo section for receiving electromagnetic radiation generated by a target in response to said transmitted electromagnetic radiation.

2. The coil system of claim 1, wherein said plurality of transmitting coils comprise at least four parallelly connected bar coils mounted on the outer surface and symmetrically about the longitudinal axis of said torpedo, each of said transmitting coils being mounted in a recess on said outer surface of said torpedo section.

3. The coil system of claim 2, wherein said plurality of receiving coils comprise two bar coils connected in quadrature and mounted internally within said torpedo section, said bar coils being mounted substantially orthogonal to said transmitting coils and being mounted substantially orthogonal to each other.

4. The coil system of claim 2, wherein said receiving coils comprise two vase coils connected in quadrature and mounted internally within said torpedo section, said vase coils being mounted substantially orthogonal to said transmitting coils and being mounted substantially orthogonal to each other.

5. The coil system of claim 2, wherein said receiving coils comprise at least two pairs of bar coils mounted internally within said torpedo section, said pairs of bar coils being mounted substantially orthogonal to said transmitting coils and symmetrically arranged about the longitudinal axis of said torpedo, said coils in each pair being connected series opposing, and said pairs being connected to each other in quadrature.

6. The coil system of claim 2, wherein said receiving coils comprise at least two pairs of bar coils mounted on the torpedo section, said pairs of bar coils being mounted substantially orthogonal to said transmitting coils in recesses on said torpedo section, and symmetrically arranged about the longitudinal axis of said torpedo, said coils in each pair being connected series 0pposing, and said pairs being connected to each other in quadrature.

7. The coil system of claim 2, wherein said receiving coils comprise at least two pairs of flat wound spiral coils mounted externally on said torpedo section, said pairs of spiral coils being substantially orthogonal to said transmitting coils, and symmetrically arranged about the longitudinal axis of said torpedo, said coils in each pair being connected series opposing, and said pairs being connected to each other in quadrature.

8. A coil system for a torpedo electromagnetic influence firing system comprising:

a plurality of transmitting coils mounted internally in a section of said torpedo for transmitting electromagnetic radiation; and

a receiving coil mounted on said torpedo section for receiving electromagnetic radiation generated by a target in response to said transmitted electromagnetic radiation.

9. The coil system of claim 8, wherein said plurality of transmitting coils comprise at least two pairs of square coils, said coils in each pair being connected in parallel, said pairs being connected in quadrature, and said pairs of square coils being mounted symmetrically about the longitudinal axis of said torpedo.

10. The coil system of claim 9, wherein said receiving coil comprises a square coil mounted internally within said torpedo section, said receiving coil being positioned substantially orthogonally to said transmitting coil and symmetrically to t he longitudinal axis of said 12. The coil system of clz n n 9, wherein said receiving l l ellie coil system of claim 9 wherein said receiving coil compris-es a bar coil -moumed internally wit-hi" Sai-d coil comprises a coil wound externally around said torgagg zjfg gf Substannany along the longnudmal axis pedo section, substantially orthogonal to the longitudinal axis of said torpedo. a: 

1. A coil system for a torpedo electromagnetic influence firing system comprising: a plurality of transmitting coils mounted on a section of the torpedo for transmitting electromagnetic radiation; and a plurality of receiving coils mounted on said torpedo section for receiving electromagnetic radiation generated by a target in response to said transmitted electromagnetic radiation.
 2. The coil system of claim 1, wherein said plurality of transmitting coils comprise at least four parallelly connected bar coils mounted on the outer surface and symmetrically about the longitudinal axis of said torpedo, each of said transmitting coils being mounted in a recess on said outer surface of said torpedo section.
 3. The coil system of claim 2, wherein said plurality of receiving coils comprise two bar coils connected in quadrature and mounted internally within said torpedo section, said bar coils being mounted substantially orthogonal to said transmitting coils and being mounted substantially orthogonal to each other.
 4. The coil system of claim 2, wherein said receiving coils comprise two vase coils connected in quadrature and mounted internally within said torpedo section, said vase coils being mounted substantially orthogonal to said transmitting coils and being mounted substantially orthogonal to each other.
 5. The coil system of claim 2, wherein said receiving coils comprise at least two pairs of bar coils mounted internally within said torpedo section, said pairs of bar coils being mounted substantially orthogonal to said transmitting coils and symmetrically arranged about the longitudinal axis of said torpedo, said coils in each pair being connected series opposing, and said pairs being connected to each other in quadrature.
 6. The coil system of claim 2, wherein said receiving coils comprise at least two pairs of bar coils mounted on the torpedo section, said pairs of bar coils being mounted substantially orthogonal to said transmitting coils in recesses on said torpedo section, and symmetrically arranged about the longitudinal axis of said torpedo, said coils in each pair being connected series opposing, and said pairs being connected to each other in quadrature.
 7. The coil system of claim 2, wherein said receiving coils comprise at least two pairs of flat wound spiral coils mounted externally on said torpedo section, said pairs of spiral coils being substantially orthogonal to said transmitting coils, and symmetrically arranged about the longitudinal axis of said torpedo, said coils in each pair being connected series opposing, and said pairs being connected to each other in quadrature.
 8. A coil system for a torpedo electromagnetic influence firing system comprising: a plurality of transmitting coils mounted internally in a section of said torpedo for transmitting electromagnetic radiation; and a receiving coil mounted on said torpedo section for receiving electromagnetic radiation generated by a target in response to said transmitted electromagnetic radiatiOn.
 9. The coil system of claim 8, wherein said plurality of transmitting coils comprise at least two pairs of square coils, said coils in each pair being connected in parallel, said pairs being connected in quadrature, and said pairs of square coils being mounted symmetrically about the longitudinal axis of said torpedo.
 10. The coil system of claim 9, wherein said receiving coil comprises a square coil mounted internally within said torpedo section, said receiving coil being positioned substantially orthogonally to said transmitting coil and symmetrically to the longitudinal axis of said torpedo.
 11. The coil system of claim 9, wherein said receiving coil comprises a coil wound externally around said torpedo section, substantially orthogonal to the longitudinal axis of said torpedo.
 12. The coil system of claim 9, wherein said receiving coil comprises a bar coil mounted internally within said torpedo section substantially along the longitudinal axis of said torpedo. 